This application claims the benefit of Japanese application No. 8/231742 filed on Sep. 2, 1996 and Japanese Application No. 8/271546 filed on Sep. 20, 1996 which are incorporated herein by reference.
This invention relates to novel humanized immunoglobulins, and is based on information about a site on Fas ligand which is important to suppress apoptosis which is induced in Fas-expressing cells through the Fas-Fas ligand interaction. Specifically, the invention relates to humanized immunoglobulins or active fragments thereof which are specifically reactive to Fas ligand. Said immunoglobulins and said site are useful in clinical applications to diseases which are provoked by apoptosis induced by the physiological reactions between Fas antigen and Fas ligand, and for example, are useful in elucidation of Fas system in cell death, in immunological therapy and diagnosis, in detection for Fas ligand, or in the related industrial fields.
The homeostasis of multicellular organisms is maintained by the growth and death of cells, which are delicately controlled. During the processes of ontogeny, a large number of cells are eliminated through cell death. Organs in adults also maintain their functions by continuously keeping the balance of the growth and death of the organ-constituted cells. Such cell death is referred to as xe2x80x9cprogrammed cell deathxe2x80x9d, which is a predetermined death, and is discriminated from accidental cell death [Raff, M. C., Nature, vol. 356, p.397-400, 1992].
These two cell deaths are different from each other in process. It has been understood that the programmed cell death is caused by apoptosis process whereas the accidental cell death is caused by necrosis process resulting in cell death [Kerr, J. F., Brit. J. Cancer, vol. 26, p.239-257, 1972].
Fas antigen is a cell surface protein which mediates the programmed cell death, apoptosis, and the cDNA of the antigen has been cloned [Nagata, et al., Cell, vol. 66, p.223-243, 1991]. The structure of the resulting cDNA has revealed that human Fas antigen is a transmembrane type protein which consists of 319 amino acid residues containing one transmembrane domain. The extracellular domain of Fas antigen consists of 157 amino acid residues and is rich in cysteine residues. Mouse Fas antigen consists of 306 amino acid residues, and shows 49.3% homology to human Fas antigen.
The structure of the extracellular domain in Fas antigen which is cysteine-rich has been demonstrated to be a well conservative structure also found in low-affinity receptors for nerve growth factor (NGF) and receptors of tumor necrosis factor (TNF), showing that Fas antigen is a cell surface protein which belongs to a family of NGF/TNF receptor. In 1993, a group of Dr. Nagata, Shigekazu and his coworkers identified the ligand molecule of rat Fas antigen [Nagata, et al., Cell, vol. 75, p.1169-1178, 1993], which had been expected to exist within the living body in the light of the fact that most proteins of this family co-exsit with their ligands in body. Subsequently, the same group identified the molecules of mouse and human Fas ligands [Nagata, et al., Int. Immunol., vol.6, No. 10, p.1567-1574, 19941.
Dr. Nagata et al. showed that Fas ligand is a protein consisting of 278 amino acids with a molecular weight of 31,138, and that it contains four N-glycosidic linkage sites and thus is a glycoprotein [Nagata, et al., Cellular Engineering, vol.13 No. 8, p.738-744, 19941]. Further, it has been shown that a soluble Fas ligand molecule induces apoptosis in target cells expressing Fas antigen on their cell surfaces (Nagata, et al., J. Exp. Med., vol. 179, p.873-879, 1994].
Hanabuchi et al. reported that the analysis on mechanism for the cytotoxicity of target cells by killer T cells via Fas antigen reveals that transmission of apoptosis signals via Fas antigen on the target cells may be responsible for the cytotoxicity of the target cells by CD4-positive T cells (CTLs) which does not express perforin, and thereby it was revealed that Fas ligand exists on the cell surface of CD4-positive CTLs [Hanabuchi, et al., Proc. Natl. Acad. Sci. USA, vol.91, No. 11, p.4930-4934, 1994].
As described above, Fas antigen appears to transmit a signal causing xe2x80x9cdeathxe2x80x9d to cells, and it has been shown that the inactivation of the proteins mediating apoptosis such as Fas antigen and Fas ligand causes the overgrowth of cells, while, on the contrary, the extraordinary activation of such proteins causes a certain inflammatory reaction.
For example, it has been reported that there is a mutation in the Fas gene of a mice which has lpr (lymphoproliferation) mutation causing an autoimmune disease-like symptom, whereas there is a mutation in Fas ligand itself of a mice which has gld (generalized lymphoproliferative disease) mutation also causing an autoimmune disease-like symptom [Nagata, et al., Cell, vol. 76, p.969-979, 1994].
Further, recent investigations have shown that the physiological reactions between Fas antigen and Fas ligand may cause various diseases.
For example, it has been reported that tat protein derived from HIV, the AIDS-causative virus, expedites the expression of Fas ligand to induce apoptosis of the T cells expressing Fas antigen, via the interaction of Fas-Fas ligand [Westerndrop, M., et al., Nature, vol. 375, p.497-500, 1995], and the expression of Fas on HIV-infected T cells has been actually found [Kobayashi, et al., Proc. Natl. Acad. Sci. USA, vol. 87, p.9620-9624, 1990]. These reports show that apoptosis induced by the interaction of Fas-Fas ligand may be one of the mechanisms of elimination of CD4-positive T cells in AIDS. Further, there are reports, each of which shows that the mice to which anti-Fas antibody (Jo-2) has been administered intra-abdominally develop fulminant hepatitis to lead death [Ogasawara, et al., Nature, vol. 364, p.806-809, 1993], that the Fas expression is observed in viral hepatitis [Hiramatsu, et al., Hepatology, vol. 19, p. 1354-1359, 1994], and that the Fas expression is also observed in diabetes mellitus and autoimmune diseases such as systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA), and therefore, it is speculated that these diseases as mentioned above would be caused by Fas ligand, which is reactive to Fas antigen.
Under the circumstances, creation of agents exhibiting suppressive (inhibitory) activity against the binding between Fas and Fas ligand to lead to suppression of apoptosis will be extremely significant for advanced exploration of the above studies and in particular, treatment of diseases in a future clinical application.
The inventors of the present invention found the mouse monoclonal antibodies which are specifically reactive to Fas ligand to suppress (inhibit) the physiological reactions between Fas and Fas ligand, and filed a patent application therefor (the Japanese Patent Application No. 303492/1995). abandoned, and to which priority is claimed by PCT Application No. WO96/29350. It has been believed that since the monoclonal antibodies bind to Fas ligand more strongly than Fas, the antibodies may inhibit the physiological reactions of Fas-Fas ligand in vivo.
It is natural that such highly active monoclonal antibodies are desirable in clinical application, but, unfortunately, non-human immunoglobulins such as the aforementioned mouse monoclonal antibodies suffer disadvantages in application to human, which are provided below. The non-human immunoglobulins show the relatively shorter half life in vivo, and require more frequent administrations to maintain the predetermined level in blood compared to human antibody. It should be noted that the non-human immunoglobulins contain an amino acid sequence which may exert antigenicity on the administration to human. Thus, in the case of frequent administration of the non-human immunoglobulins to human, an immune response elicited by the administration eliminates the immunoglobulins administered at the later stages, and ultimately may cause anaphylaxis-like shocks.
In order to resolve the above problems, so called chimeric antibody, an immunoglobulin having a constant region from human immunoglobulin combined to a variable region from mouse immunoglobulin has been created [LoBuglio, et al., Proc. Natl. Acad. Sci. USA, vol. 86, p.4220-4224, 1989]. This described that the half life of the chimeric antibody in human was prolonged six times compared to the mouse antibody, but the period is still only about ⅕ of that of the common human immunoglobulin. Also, the article reported that the immune response to the chimeric antibody was observed in one of three patients receiving the chimeric antibody. This immune response was believed to be derived from the variable region from the mouse immunoglobulin since the response could be absorbed when anti-mouse immunoglobulins were reacted with the chimeric antibody.
To resolve the problem which could not be overcome by the chimera technique with human immunoglobulin, Winter, et al. reported the process for constructing humanized immunoglobulin which is more analogous to the human immunoglobulin than the chimeric antibody, which comprises transplanting the complementarity determining region (hereinafter may be referred to as CDR) directly binding to an antigen, which is within the variable region (V region), into the CDR in the variable region of human immunoglobulin according to genetic engineering techniques [Winter, et al., Nature, vol. 321, p.522-525, 1986].
As reviewed in Bendig, A Companion to Methods in Enzymology, vol. 8, p.83-93, 1995, diverse humanized immunoglobulins have been previously prepared by procedures as mentioned above. However, compared to the original mouse immunoglobulins, which are donors of the CDR, most of humanized immunoglobulins involve significant decrease in their activity, and several maintain the same activity, above all, very few show the higher activity. Needless to say, no reports describe any preparation of a humanized immunoglobulin directed to Fas ligand according to the present invention.
The recent investigation has reported a putative three-dimensional structure of mouse Fas ligand [Manuel C. P., et al., Molecular Immunology, vol. 32 (10), p.761-772, 1996]. In this report, the authors believed that mouse Fas ligand should form a trimer structure to exhibit its biological activity similarly to TNF-xcex1 and TNF-xcex2 (hereinafter referred together to as TNF, simply), and, making reference to the structure of TNF trimer and the interaction site between TNF and TNF receptor, they predicted a interaction site between mouse Fas ligand monomers, and a interaction site between mouse Fas ligand and Fas antigen, after preparation of a trimer model for mouse Fas ligand. However, this prediction has not been supported therein any more.
On the other hand, any putative three-dimensional structure model for human Fas ligand as shown in the above literature has not been reported, and there have been no reports that show the interaction site between the Fas ligand monomers and the interaction site of the Fas-Fas ligand. Under the circumstances, it has been still unknown which regions in Fas ligand or Fas should be targeted to suppress (or inhibit) apoptosis induced by the physiological reactions of Fas-Fas ligand.
The decrease in the activity of humanized immunoglobulin compared to the original mouse immunoglobulin is believed to be mainly due to less antigen-binding activity induced by structural change in the CDR to be transplanted, which change is on the basis of the difference in stereochemical structure of the framework region between mouse immunoglobulin as CDR donor and human immunoglobulin as CDR acceptor. In order to avoid such decrease in the activity, any modification is required in the process for humanization of an antibody by CDR transplantation.
The monoclonal antibodies specifically reactive to Fas ligand which are encompassed within the scope of the invention of the Japanese Patent Application No. 303492/1995, have the useful activity to suppress (or inhibit) the physiological reactions between Fas and Fas ligand. However, the antibodies are a mouse monoclonal antibody, and therefore, cannot be practically applied to the clinical field of human in the light of the safety (induction of antigenicity) and the efficacy (shortening of half life).
As a major embodiment, the present invention provides humanized immunoglobulins or active fragments thereof which are specifically reactive to Fas ligand, and in particular, provides humanized immunoglobulins which are specifically reactive to Fas ligand to be able to suppress (or inhibit) the physiological reactions between Fas and Fas ligand.
So far, the interaction site between human Fas and Fas ligand has not been shown, and a modelling or a crystal structure analysis for the Fas-Fas ligand complex has not been performed, and therefore, it has been impossible to identify a site to effectively suppress (or inhibit) apoptosis induced by the physiological reactions of Fas-Fas ligand.
As another embodiment, the present invention demonstrates for the first time a site on human Fas ligand associated with apoptosis-suppressing activity, by means of examining the reactivities of diverse Fas ligand molecules introduced with an amino acid substitution (Fas ligand variants) with diverse anti-Fas ligand monoclonal antibodies having the high apoptosis-suppressing activity, constructing a molecular model for the human Fas ligand trimer, and further confirming the distribution of the site identified in the above experiment within the human Fas ligand trimer.